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Build a Mini Greenhouse with an Old Window

Updated: Feb. 22, 2023

Give an old window new life by turning it into a mini greenhouse.

mini greenhouse with old windowFamily Handyman
Whether you want to prolong your growing season or get a jumpstart on spring planting, this mini greenhouse is for you. Start with some cedar boards and a few basic power tools, and you can knock out this outdoor project in just a couple of hours!

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How to Build a Greenhouse from Old Windows Materials & Tools

Note: The amount of wood that you will need for the greenhouse is determined by the size of the window.

  • Window
  • Vintage hinges (2)
  • 1 x 5-1/2 cedar board (5)
  • 1 x 4 cedar board (3)
  • 1 x 2 cedar board
  • 1-5/8-in. exterior screws
  • Hinge screws
  • Miter saw (optional)
  • Circular saw
  • Drill/driver

Cut the Parts

mini greenhouse measure window

For this how to build a greenhouse from old windows project, I searched a local salvage yard for the perfect window. The one I purchased measures 28 x 23-1/4 in. and features a grid pattern with crackled white paint. I didn’t trim the wood window or alter it in any way for this project to preserve its vintage charm. The following steps will show you how to build a mini greenhouse based on a window this size.

mini greenhouse cut parts

First, cut four 1 x 5-1/2 in. boards to 25-1/4 in. for the bottom of the box. Then rip one of these boards to 4-1/4-in. wide. Next, cut two front boards and three back boards to 27-1/2 in. Then cut four side boards to 21 in.; the angled side pieces will be cut later on.

Cut the following amounts and lengths of 1×4 for all brace pieces: two at 20-3/4 in. for the bottom, two at 8-3/4 in. for the front, two at 8-3/4 in. for the front sides, two at 14 in. for the back and two at 13 in. for the back sides.

Assemble the Box

mini greenhouse measure bottom

mini greenhouse braces on bottom

mini greenhouse assemble base

Layout the bottom pieces and the first course of front, back and two side pieces as shown. Screw the two 20-3/4 in. brace pieces to the bottom boards along the sides to hold them together; then screw the front, back and side pieces together and to the bottom.

mini greenhouse assemble second course

Separately, screw together the second course of front, back and side pieces. Then stack the assembly on top of the first course that you created earlier.

mini greenhouse front brace pieces

Lay the box on its side to screw on the front and front side brace pieces.

mini greenhouse back brace pieces

Turn the box so that the back is flat on the work surface; then add the third back piece and screw on the two back brace pieces.

mini greenhouse angled side pieces

To angle the window lid of the greenhouse, which allows more sunlight to reach the plants inside, cut two angled pieces of 1 x 5-1/2 in. board. To find the measurements for the angled pieces, turn the box right side up and carefully place the window on top of the entire assembly, as shown. Measure the back, bottom and front of the openings and mark the measurements on a 1 x 5-1/2 in. board. Use a straightedge to connect the top of the back marks and the top of the front marks. Then cut out the two pieces.

mini greenhouse adding angled side pieces

Carefully remove the window and screw the angled side pieces to the top back piece. Add the back side brace pieces to the inside of the box. I added screws through the small part of the angled pieces into the second course, too, for a little extra stability.

mini greenhouse add hinges to window

mini greenhouse screw hinges to back of box

Next, add the window lid. Mark where you want the hinges and screw them in place on the window. Place the window on the box and screw the hinges to the back. The last thing to do is to cut a piece of 1×2 board to fit inside the mini greenhouse. Then you can prop up the window lid as you tend to your cozy plants!

Click here to learn about 10 awesome vegetables to grow yourself.